Conventional NC machines are classified into three types, namely, one in which all control data is inputted in the form of punched tapes, another in which data to be punched is inputted by keying, and the other in which actual machining is performed and the data resulting therefrom is stored. However, the first two types necessitate programing in detail the movement of the object to be controlled by using a particular NC language and take much labor and time in preparing punched tapes and also present problems in tool setting. In the third type, the skill of the operator in doing the actual work greatly influences the subsequent operation and there are various disadvantages in the control operation, so that this type has not been in wide use.
Thus, the applicant has previously proposed a device described in U.S. Pat. No. 4,033,206 as means for eliminating the drawbacks described above. This device is characterized by effecting the inputting of data by digital switches rather than by tapes, minimizing the number of steps of inputting data and simplifying the inputting operation. To this end, the device is so arranged that the machining shape and finishing shape and size to be imparted to the blank and machining conditions are inputted, with the mode for movement of the tool being fixed. The advent of this type of device has completely eliminated the drawbacks in the prior art.